1. Field of the invention
The present invention relates to a gas exchange apparatus employing the silicone membrane hollow fiber for use as an artificial lung itself by being connected to the external blood circulation circuit, an artificial "ERA" as a liquid-to-gas phase gas exchanger, and further an oxygenator and disoxidizer for liquid and gas.
2. Brief Description of the Prior Art
As a conventional gas exchanger, there has been known a membrane-type artificial lung disclosed in Japanese Patent Publication No. 3-60508 (1991), in which gas exchange operation is performed through a porous gas exchange membrane having a plurality of minute or fine openings formed therethrough and serving as gas flow passages, wherein a kind of fine particles are maintained in the fine openings to reduce the sectional area, and, in addition, an anti-coagulant for blood is retained in the fine particles themselves or between these particles. Such a retention function of the agent contributes to prevent leakage of components of blood, such as water during a long term circulation. Such a retention function also prevents production of thrombus on the surface of gas exchange membrane, thereby the out-body circulation being enabled with a small amount of heparin supplement.
Another gas exchanger is disclosed using a "silicone membrane hollow fiber having a wall thickness of 50 to 150 micron", such as an anti-thrombus fiber type artificial lung disclosed in Japanese laid-open patent publication No. 63-97172, in which a hydrophilic monomer is graft-polymerized on the surface of a hollow fiber membrane, which is received in a housing, wherein blood is allowed to flow outside the hollow fiber membrane, and an oxygen-containing gas is allowed to flow inside the membrane. Using this artificial lung, since blood is allowed to come in contact with the outer surface of the membrane, the surface of which being anti-thrombus treated, the production of thrombus is advantageously hardly caused.
However, the gas exchange rate was not satisfactory in either of the conventional gas exchanger, since fine particles are confined in fine openings using "porous hollow fiber" for preventing sealum leakage in the first example, and "silicone membrane hollow fiber" having an increased wall thickness is used in the second embodiment. Therefore, there have been problems, when the exchange rate is increased, the dimension of the apparatus, that is, of the artificial lung increases, resulting in an increased quantity of blood, namely the priming volume, which is filled in the apparatus. In contrast, the reduced priming volume, although providing a small size, the quantity of gas exchange is accordingly decreased, and, therefore, the gas exchange rate is lowered.